1. Field of the Invention
The invention relates to a power converter connected in single-phase mode. The invention applies more particularly to a power converter provided with a controlled current source.
2. Description of the Related Art
As is known, a power converter includes a number of input phases connected to the network, for example three input phases if it is connected in three-phase mode or two input phases if it is connected in single-phase mode. Connected to its input phases, a power converter includes a rectifier stage for transforming the AC voltage supplied by the network into a rectified voltage. The converter also includes a power supply bus provided with a first power supply line with positive potential and a second power supply line with negative potential to which is applied the rectified voltage and a bus capacitor connected between the first power supply line and the second power supply line and intended to keep the DC voltage on the bus constant.
It is known practice to place a controlled current source in series on the first or second power supply line of the DC bus, upstream of the bus capacitor. This current source includes, for example, an inductance and an electronic converter connected in series, said electronic converter having two parallel switching arms and a capacitor. The switching arms of the electronic converter are controlled to modulate the voltage at the terminals of the capacitor of the electronic converter in order to obtain, at each instant, a determined voltage at the terminals of the electronic converter, thus making it possible to control the current at the output of the rectifier stage, called rectifier current, and to act on the input current supplied by the network.
When such a power converter is connected to the network in three-phase mode, its electronic converter is controlled in modulation in a so-called continuous operating mode which is applied to the rectifier stage and in which the voltage at the terminals of the capacitor of the converter must always satisfy the following condition:VC≧max|Vr(t)−Vbus(t)| with Vr(t)=Vred(t) and <Vbus>=<Vred>,in which:                Vr(t) is the theoretical rectified voltage of the network. When the rectifier stage is conducting, the voltage Vr is the same as the real rectified voltage Vred.        <Vbus> is the average voltage of the bus and <Vred> the average voltage at the output of the rectifier stage.        
Thus, it is possible to guarantee a constant rectifier current. In this mode of operation, the voltage of the DC power supply bus will be 95.5% of the peak voltage applied at the output of the rectifier stage.
On the other hand, when this power converter is connected to the network in single-phase mode, this continuous operating mode is not applicable because the voltage of the DC power supply bus is then 63.7% of the peak voltage of the network. As it happens, this voltage level cannot be used to control a motor.